Yielding work center



May 3, 1,938. s. w. BATH- YIELDING WORK'CENTER Filed June l, 19:56

lv. W wwwa um, NN g mm .Q1 NN. um l N NNI, NN mw 13a-enige May 3, 193s UNITEb STATES l yrELnrNG wom: CENTER stanley w. nath.) Shrewsbury, Mass., assignmte John Bath & Company, Worcester, Mass., a corporation of Massachusetts Animation June 1, 193e, serial Nn. casos ZCIaims.

This invention relates to centers for supporting a piece of work in a machine tool. The invention possesses special advantages when used Ain a grinding machineunder conditions such that a slight yield of -the Work away from the wheel is at times desired, in order to protect thewheel from excessive wear or breakage. Such conditions arise, for instance, in the grinding of longitudinal flutes in taps or other similar tools. It is the general `object of my invention to -provide awork center .which will normally support the work in a predetermined axiahposition,

but'which on occasion will yield slightly in any radial direction to relieve excessive wheel pressure on the work.

A further object of my invention is to provide I a construction in which the resistance of the center to yielding displacement may be regulated and adjusted as desired., My invention further relates to arrangements and combinations of parts which will be hereinafter described and more particularly pointed out in the appended claims..

A preferred form of the invention is shown in the drawing, in which Fig. 1 is a ,front elevation, `partly in section, showing my linvention in operative relation -to a grinding wheel and work piece;

Fig. 2 is a front elevation," partly in section,

so showing the parts in normal axial alignment;

Fig. 3 is an end view, looking in the direction of the arrow 3 in Fig. 2;

Fig. 4 is a partial side elevation of the holder; and

35 Fig. 5 is a side elevation of the yielding center.

Referring to the drawing, I have indicated a' tap T supported `on a tail center Il and a yielding head center II, and engaged by a grinding wheel W. The tail center I0 is commonly mount- 40 ed in fixed axial position in a suitable tail stock (not shown). The head center II is mounted in a holder I2 which is commonly inserted in a tapered opening in a work spindle I4 mounted for angular movement in a head stock, (not 45 shown).

The holder I2 is provided with an axial recess I6 in its outer end, and also with an axially disposed conical depression II in the inner end wall IB of the recess I6. The holder is also provided 50 with a plurality of radially disposed openings 2li, equally spaced angularly and threaded to re ceive headless set screws or plugs 22 preferably having small axial projections 23 at their ends. The center II is provided rwith a-cylindrlcal 55' .portion 30 which is veryv loosely received in the recess I6, and'with a conical inner end portion 3l adapted to be seated in the conical depression I1 in the holder. It will be noted, however, that the angle of the part 3I. is more acute than the angle of the` depression I1, so that the center II 5 may' rock freely about the point of the conical end portion 3 I The cylindrical portion 30 of the center II is also provided with radially disposed openings 32, equally spaced anguiarly and corresponding in 10 number to the t eadd openings 20 in the holder.

In the drawing four such openings are shown but a larger or smaller number may beused if desired.

Relatively stiff coil springs 33 are mounted in 15 the openings 32, after the holder and center are assembled, and the outer ends of these springs receive the projections 23 on the plugs` 22 and are centered thereby. The plugs 22V e then relatively adjusted fso that the spr ngs'cause the 20 center II to assume its normal position in axial alignment with the holder I2. lIn this normal position, the springs 33 are held firmly but without substantial compression by the plugs 22.

The center II is also provided with an outwardly extending flange 35 having an offset edge `portion 36 which loosely embraces the enlarged` cylindrical portion of the holder I2 and assists in excluding dirt therefrom.

Having described the details of construction of my improved yielding center, the method of operation and advantages thereof are as followsz- When producing fiuted work such as taps,'the flutes are commonly roughed out with a milling cutter before' the taps are hardened and the utesare then ground after the hardening operation. In grinding these flutes, the wheel enters at the small end of the tap (shown at the right.

.in Fig. 1) and travels along the flute to the 40 point where the milling cut terminates. This point is not very definitely fixed and varies somewhat in different taps. y

When the grinding wheel W reaches the end of the flute, an-excessive pressure will be thrown on the wheel if the flute is short. Under these conditions my improved yielding center will allow the work to be depressed by the wheel as indicated in Fig. 1, thus relieving the strain on the wheel and preventing excessive wear or damage thereto. As vsoon as the wheel pressure is removed, the center restores the work to normal axial position.

With the springs equally spaced angularly, the. center will yield with substantially the same resistance in any direction, so that the .holder maybe indexed to diierent angular positions without changing the yielding action.

Having thus described my invention and the advantages thereof, I do not wish to be limited to the details herein disclosed, otherwise than as set iorthin the claims. but what I claim is:-

1. Work supporting means having a vertically iixed center for one end of a piece of work and a yielding work center for the other end oi' said piece of work, said yielding work center comprising a rmly supported holder having an end recess. a center element loosely mounted in said recess and Vhaving an outer end portion thereof abutting and supporting the adjacent end of said work piece, and yielding means to hold said center element in substantial axial alignment with ananas 'said holder and with'said work-piece, the abutting portions of said center element and of said work piece being yieldabie under pressure out of such axial alignment while said holder, fixed center and the other end of the work piece remain in original alignment, and said abutting portions being automatically returned to original alignment when the pressure is removed.

2. Work-supporting means as set forth in claim 1, in which the recess in the holder has a conical depression in its inner end wall and in which the center element has a conical end portion seated in said conical depression and has a second conical end portion engaging and supporting the adjacent end of the work piece.

STANLEY W. BATH. 

